The present invention generally relates to medical catheters. More particularly, the present invention relates to a combination device comprising two catheters, or a dual catheter assembly, for use in vascular procedures wherein the shaft of the first catheter functions as a guidewire for the second catheter.
Although used in a variety of medical procedures, multiple balloon catheters are most widely associated with percutaneous transluminal coronary angioplasty. The procedure typically involves advancing a balloon catheter to the partially blocked coronary artery and inflating one or more balloons at the blockage site. The inflated balloons stretch and/or fracture the blockage thereby enlarging the opening of the occluded vessel. In some cases, a stent is also deployed to further enlarge the opening and to prevent the weakened vessel from collapsing.
In general, separate balloon catheters are used for performing angioplasty and for delivering stents. As a result, a physician performing angioplasty followed by stent implantation may use multiple devices. For example, the procedure may start with a floppy tip guidewire followed by a low profile balloon catheter riding over the guidewire to predilate an occluded vessel. Once the vessel is predilated, progressively larger balloon catheters may be navigated to the stenosis, used and then withdrawn in succession to sufficiently enlarge the opening. Finally, another balloon catheter bearing a stent may be used to deliver the stent to the lesion site.
Attempts have been made to design devices that perform more than one function during vascular procedures. For example, U.S. Pat. No. 5,035,686 discloses a low profile balloon on a wire catheter that is designed to also act as guidewire for a second catheter. Because the low profile balloon catheter may also function as an independent guidewire, it would remain in the vessel and any subsequent catheter would be threaded over its shaft. However, because the subsequent devices are necessarily off-the-shelf catheters often made by different manufacturers, the desired combination of catheters either may not work well together, or may not be compatible with each other.
Another example of a catheter that performs more than one function is described by U.S. Pat. No. 5,226,889 which discloses a multiple balloon catheter wherein one of the balloons carries a stent. The idea behind this device is that this single catheter may be used for performing both angioplasty and stent delivery. However, multiple catheters are still required in most cases. Due to the stent, these combination catheters typically have larger profiles and thus are not generally able to navigate the occluded vessel without the vessel being pre-dilated. Depending on the nature and extent of the occlusion, more than one successively larger balloon catheter may be required to sufficiently open the blockage so that it may accommodate the larger profile of the combination catheter.
In summary, a product that is designed to be used for all aspects of angioplasty and stent delivery would be desirable. Because predilation and stent delivery may be performed with a single product, the use of such a device would maximize efficiency and minimize catheter exchange.